Master student Projects

From LHCb Wiki
Jump to: navigation, search

Projects for Master students in the Nikhef B-physics (LHCb) group 2017 - 2018

date: Dec 2017

This is an overview with all available Master student projects in the Nikhef B-physics (LHCb) group.

If you have your own research proposal, need more detailed information on the (availability) of individual proposals or would like to discuss about other available projects in the group you are always welcome to contact either the contact person for the project and/or the Nikhef B-physics group leader:

Marcel Merk [e-mail:, Tel 020-5925107, Nikhef room N243]

For an overview of the theses written in the Nikhef B-physics group you can look at the Nikhef LHCb theses page

(The full list of projects at Nikhef can be found here.)

Master projects in the Nikhef B-physics group

1) Searches for new pentaquarks

Supervisor : P. Koppenburg (staff)

Research Description:

In 2015 LHCb surprisingly discovered states containing five quarks, called Pc+ pentaquarks. Such particles question our understanding of confinement, the principle that forces quarks to remain in a single hadron. Which hadrons are allowed and which are not? The pentaquarks were found in the decay of the Lambda_b baryon to a Pc+ and a kaon, and Pc+ to a J/psi and a proton. This project aims at studying other similar but yet unobserved decays which could reveal the presence of the know Pc+, or yet unknown pentaquarks. The student will optimise a selection for finding such a decay in LHCb data using machine learning techniques.

Relevant information:

[1] arXiv:1507.03414 (the pentaquark paper)

[2] arXiv:1406.0755 (a paper by P. Koppenburg similar to what the project could lead to).

2) Measurement of BR(Lb -> p Ds-)

Supervisors: Niels Tuning (staff), Lennaert Bel (PhD) , Mick Mulder (PhD)

Research description:

This project aims to discover the branching fraction of the decay Lb->p Ds+. The decay Lb->p Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark. It has not been measured yet (although some LHCXb colleagues claim to have seen it in the past).

This decay is interesting, because
1) It is sensitive to the CKM-element Vub, which determination is heavily debated.
2) It can quantify non-factorisable QCD effects in b-baryon decays.

The decay is closely related to B0->pi-Ds+, which proceeds through a similar Feynman diagram. Also the final state of B0->pi-Ds+ is almost identical to Lb->p Ds+. The aim is to determine the relative branching fraction of Lb->pDs+ with respect to B0->D+pi- decays, in close collaboration with the PhD (who will study BR(B0->pi-Ds+)/BR(B0->D+pi-) ). The aim is that this project results in a journal publication on behalf of the LHCb collaboration. For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. This is a project that is closely related to previous analyses in the group. Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.

Relevant information:

[1] R.Aaij et al. [LHCb Collaboration], ``Study of the kinematic dependences of Lambda_b production in pp collisions and a measurement of the Lambda_b->Lambda_c pi branching fraction, JHEP 08 (2014) 143 [arXiv:1405.6842 [hep-ex]].

[2] R.Aaij et al. [LHCb Collaboration], ``Determination of the branching fractions of B0s->DsK and B0->DsK, JHEP 05 (2015) 019 [arXiv:1412.7654 [hep-ex]].

[3] R. Fleischer, N. Serra and N. Tuning, ``Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States, Phys. Rev. D 83, 014017 (2011) [arXiv:1012.2784 [hep-ph]].

[4] K. de Bruyn, R. Fleischer, R. Knegjens, M. Merk, M. Schiller and N. Tuning, ``Exploring Bs -> Ds(*)K Decays in the Presence of a Sizable Width Difference Delta Gamma_s, Nucl. Phys. B 868, 351 (2013) [arXiv:1208.6463 [hep-ph]].

3) Measurement of BR(B0 -> pi Ds-)

Supervisors: Niels Tuning (staff), Lennaert Bel (PhD) , Mick Mulder (PhD)

Research description:

This project aims to measure the branching fraction of the decay B0->pi Ds+. This decay is closely related to Lb->p Ds+ (see above), and close collaboration between the two master projects is foreseen. This research was started by a previous master student. The new measurement will finish the work, and include the new data from 2015 and 2016.

Relevant information:

[1] Master Thesis, Mick Mulder, 2015.

4) A search for heavy neutrinos in the decay of W at LHCb

Supervisors: Wouter Hulsbergen (staff), Elena Dall'Occo (PhD)

Research description:

Neutrinos are arguably the most mysterious of all known fundamental fermions as they are both much lighter than all others and only weakly interacting. It is thought that the tiny mass of neutrinos can be explained by their mixing with so-far unknown, much heavier, neutrino-like particles. In this research proposal we look for these new neutrinos in the decay of the SM W-boson using data with the LHCb experiment at CERN. The W boson is assumed to decay to a heavy neutrino and a muon. The heavy neutrino subsequently decays to a muon and a pair of quarks. Both like-sign and opposite-sign muon pairs will be studied. The result of the analysis will either be a limit on the production of the new neutrinos or the discovery of something entirely new.

5) A Scintillator Fibers Tracker

Supervisors: Antonio Pellegrino

Research description:

The LHCb collaboration is upgrading the present tracking system constructing a new tracker based on scintillating fibers combined with silicon photo-multipliers (SiPM): the SciFi Tracker! Nikhef plays a key role in the project, as we will build the SciFi fibers modules, the cold-box enclosure housing the SiPMs, and a large part of the on-detector electronics. In all these areas, interesting test hardware and software has to be realized, and several research topics for a Master project are available, taking the student in contact with state-of-the-art particle detectors, in a large team of physicists and engineers. Possible collaborations with the Nikhef R&D group can also be envisaged.

6) The Z forward backward asymmetry

Supervisors: Wouter Hulsbergen

Research description:

The forward backward asymmetry of Z->mumu decays probes the standard model weak mixing angle, providing a strong test of the standard model. A dominating systematic uncertainty in this measurement is the affect of detector misalignments. In this project Z->mumu events are used to improve the detector alignment and thereby increase the precision of the run-2 measurements.

7) Construction of the velo upgrade detector

Supervisors: Wouter Hulsbergen

Research description:

Nikhef contributes to the upgraded LHCb detector (installation 2019-2020) with the construction of vertex detector modules. In this project the student participates in the construction at Nikhef, in particular in R&D studies to determine the optimize the ‘gluing’ process (early 2018), and the analysis of the first test data taken with built modules (spring/summer 2018).

8) *Probing the dark sector with Y(1S)->4mu events*

Supervisors: Wouter Hulsbergen

Research description:

In certain parts of their parameter space Hidden Valley theories predict upsilon decays to two new dark sector particles that subsequently decay into two muons. These particles may or may not be long-lived. In this project we search for such events in LHCb run-2 data using the Turbo stream.

9) Measurement of the relative efficiency of muons and electrons with J/psi->ll decays

Supervisors: Patrick Koppenburg

Research description:

LHCb has produced intriguing results hinting at violation of lepton universality. As extraordinary claims require extraordinary evidence we propose to perform a measurement of the relative reconstruction efficiency of electrons and muons by comparing the number of J/psi particles counted in the di-electron and di-muon final states.

10) Very rare decays of B mesons

Supervisors: Marcel Merk

Research description: Decays of B-mesons to a pair of muons or a pair of electrons are very strongly suppressed in the Standard Model. As a consequence these decays are sensitive to virtual contributions of particles beyond the Standard Model. The project includes a theoretical study on these sensitivties and/or experimental improvements to the measurement.

Personal tools